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Oklahoma earthquake: More aftershocks, no major damage reported

November 6, 2011 | 8:54
am

Aftershocks continue to rattle Oklahoma on Sunday morning after a swarm of weekend quakes, including the largest in state history, buckled a highway, damaged several homes and gave residents the jitters.

Emergency officials and seismologists are surveying the damage following the record magnitude-5.6 earthquake Saturday night. The largest aftershock of 4.0 was reported at 3:40 a.m. CST Sunday, according to Paul Caruso, a seismologist with the U.S. Geological Survey in Golden, Colo.

The USGS is installing more sensors in the region to better analyze the quake series.

The largest quake, which occurred at 10:53 p.m. CDT, according to the U.S. Geological Survey, caused major damage to at least five homes, mostly when chimneys caved in, according to Aaron Bennett, a dispatcher with the Lincoln County emergency management. His office covers the area surrounding the epicenter near Sparks, Okla., about 55 miles northeast of Oklahoma City.

One man was reportedly injured when he tripped and hit his head while attempting to flee his home near Prague, Okla., according to local dispatchers. Prague Community Hospital did not report any other injuries associated with the quake.

U.S. Highway 62 buckled in at least two places during the quake, causing a sinkhole east of Meeker, Okla., but road crews repaired the damage overnight, Bennett said.

The quake damaged a 40-foot spire at St. Gregory University in Shawnee and ruptured a water pipe in Chandler, Okla., dispatchers said.

So many people logged on to the USGS web page to report the earthquake, Caruso said, "It crashed our response page." The last time that happened was during the 5.8 earthquake that shook Virginia in August, he said.

Saturday night's quake followed a 4.7 quake earlier in the day. Both occurred on the Wilzetta fault, or Seminole uplift, where rocks moved sideways similar to the San Andreas fault, according to Austin Holland, a research seismologist with the Oklahoma Geological Survey based at the University of Oklahoma in Norman.

The state's last big quake, a 4.3 temblor in October 2010, was along the same fault, he said.

"Faults go through cycles. In California, they see that a lot. Stress takes time to build up. It's just our sequence takes more time to build up," Holland said.

He said it was not clear what caused Saturday's two large quakes.

"We don't know enough about this fault system to say," he said.

Holland said his office has three seismic stations with seismometers positioned along the fault, and students were out Sunday morning setting up seven more, "to see what we can find out from any further seismic activity."

There were at least ten aftershocks of 3.0 or more since the quake last night, he said, and "there's many, maybe hundreds, that are going unfelt."

Oklahoma typically has about 50 earthquakes a year, but last year there were more than 1,000, prompting researchers to install seismographs in the area of the fault. It isn't clear what caused the increase, he said.

Holland said he hopes residents will respond by preparing earthquake kits and undergoing earthquake preparedness training to avoid injuries like those sustained by the Prague man who fled his home instead of ducking for cover.

"I think the awareness is growing," he said. "People need to know what to do."